How is slant distance to the DME ground station calculated?

The calculation of slant distance to the Distance Measuring Equipment (DME) ground station is accomplished by comparing and decoding signals emitted by both the aircraft and the DME ground station. When the aircraft sends a signal to the DME ground station, the station responds with a signal that the aircraft receives. The time it takes for this round-trip communication provides the necessary information to determine the distance.

This method of signal comparison is essential because it accounts for the actual path the signal takes, which is not a straight line when altitude is considered, thus allowing for the calculation of slant distance rather than just horizontal distance. The sophisticated technology employed by DME enables accurate measurements essential for navigation, particularly in situations involving varying altitudes.

Other methods mentioned, such as measuring the aircraft's altitude above ground, the distance from the last waypoint, and comparing ground speed and time to station, do not directly provide the slant distance. They may offer valuable information regarding the flight's position or trajectory, but they do not yield the precise slant distance that the DME system is specifically designed to calculate through signal analysis.